The field of the disclosure relates generally to a motor controller for electric blower motors and, more specifically, a motor controller that enables approximately constant airflow production from a backward-curved, forward-curved, or radial electric blower.
At least some electric motors are torque-calibrated when manufactured to ensure the torque output at the drive shaft of the electric motor matches the torque commanded. At least some electric motors, particularly electric motors driving blowers, such as a forward-curved blower, are further calibrated to produce approximately a constant airflow during operation in either a torque-control mode or a speed-control mode. Such a calibration, or characterization, quantizes airflow output for a given speed and torque output when driving the blower. The actual airflow output can vary according to the blower construction or duct, space, or other airflow restriction, into which the airflow is directed.
Constant airflow heating, ventilation, and air conditioning (HVAC) systems improve thermal comfort and energy savings. Constant airflow systems may also be used in certain refrigeration systems. In a constant airflow system, a motor controller for an electric blower motor receives an airflow rate demand, e.g., a value in cubic feet per minute (CFM), and then determines, e.g., by a polynomial or constant airflow algorithm, an appropriate motor torque or motor speed to produce approximately the airflow demanded. In a torque-controlled implementation, for example, motor torque is regulated based on a monitored motor speed to produce the approximate airflow.
It is desirable to utilize a backward-curved, or backward-inclined, electric blower in constant airflow HVAC systems to improve efficiency of the electric blower. Backward-curved blowers generally produce a given airflow at a higher speed and with reduced power relative to radial or forward-curved counterparts. However, such backward-curved blowers may produce multiple different airflows when operated at a given torque and speed, particularly at high airflow values. Consequently, a motor controller using known constant airflow algorithms cannot effectively operate a backward-curved electric blower to produce a demanded airflow by operating in a traditional torque-control or speed-control mode. A motor controller that overcomes this limitation for a backward-curved electric blower is desired.